The long term objective of the proposed study is to elucidate the mechanism of insulin action in the human body, and thus contribute toward improvement of the clinical treatment of diabetes. The specific objective is to demonstrate the mechanism by which insulin stimulltes sugar transport across the plasma membranes of certain cell types, including muscle and adipose tissue. We plan a three-phase approach to the problem. In the first phase, we will study the general characteristics of the transport mechanism in fat cells. In the second phase, we will study the transport mechanism in vesicles prepared from the plasma membranes of muscle or fat cells. In the third step, we will try to reconstitute the hormonal action in a cell-free system.